Although the Ministry of Economic Development unit is keeping mum about the bidders, it is believed existing players that bid included Canadian-listed junior TAG Oil and NZ private company Greymouth Petroleum.

A study group, involving some locally-based and some potentially new overseas players, also looked at the 12 blocks on offer, though it is not known if they made bids as a single joint venture or separately.

Crown Minerals group manager Chris Kilby said he was pleased with the response to the largest onshore Taranaki blocks offer in years.

"Given the blocks offer assessment process, we are unable to give you specifics at this time. Though I can confirm there was a very strong response of local and overseas bidders," he told PetroleumNews.net from Wellington.

"Officials have now started the process of evaluating bids (but) the need to ensure confidentiality of the bid evaluation process, and the need to protect commercially sensitive information concerning bids and bidding parties, means we cannot comment on how many bids were received or who the bidding parties were," Kilby added.

Crown Minerals typically takes eight weeks or so to assess block bids and to award new exploration licences.

The New Zealand Government offered nine onshore Taranaki blocks last December, then added three more in January, making the offer the largest in more than 20 years.

Energy Minister Harry Duynhoven had called for bidders to set aggressive work programs to unlock the region's hydrocarbon potential, particularly the Eocene-aged deep gas plays.

He said then that some previously held small blocks had been aggregated to provide explorers with blocks of material size that contained a broad range of exploration opportunities.

The onshore-nearshore Taranaki Basin has more than 10 producing gas-condensate and oil fields, which Crown Minerals says have proved and probable reserves of over 183 million barrels of oil and condensate and 2.16 trillion cubic feet of gas.